Steps in the hysteresis of a high spin molecule

We report the first observation of steps in the hysteresis loop of a high¿spin molecular magnet. We propose that the steps, which occur every 0.46 T, are due to thermally assisted resonant tunneling between different quantum spin states. Magnetic relaxation increases dramatically when the field is in the neighborhood of a step. A simple model accounts for the observations and predicts a value for the anisotropy barrier consistent with that inferred from the superparamagnetic blocking temperature

Type I IFN-mediated regulation of IL-1 production in inflammatory disorders.

Although contributing to inflammatory responses and to the development of certain autoimmune pathologies, type I interferons (IFNs) are used for the treatment of viral, malignant, and even inflammatory diseases. Interleukin-1 (IL-1) is a strongly pyrogenic cytokine and its importance in the development of several inflammatory diseases is clearly established. While the therapeutic use of IL-1 blocking agents is particularly successful in the treatment of innate-driven inflammatory disorders, IFN treatment has mostly been appreciated in the management of multiple sclerosis. Interestingly, type I IFNs exert multifaceted immunomodulatory effects, including the reduction of IL-1 production, an outcome that could contribute to its efficacy in the treatment of inflammatory diseases. In this review, we summarize the current knowledge on IL-1 and IFN effects in different inflammatory disorders, the influence of IFNs on IL-1 production, and discuss possible therapeutic avenues based on these observations.

Resonant spin tunneling in small antiferromagnetic particles

The paper reports a detailed experimental study on magnetic relaxation of natural horse-spleen ferritin. ac susceptibility measurements performed on three samples of different concentration show that dipole-dipole interactions between uncompensated moments play no significant role. Furthermore, the distribution of relaxation times in these samples has been obtained from a scaling of experimental X" data, obtained at different frequencies. The average uncompensated magnetic moment per protein is compatible with a disordered arrangement of atomic spins throughout the core, rather than with surface disorder. The observed field dependence of the blocking temperature suggests that magnetic relaxation is faster at zero field than at intermediate field values. This is confirmed by the fact that the magnetic viscosity peaks at zero field, too. Using the distribution of relaxation times obtained independently, we show that these results cannot be explained in terms of classical relaxation theory. The most plausible explanation of these results is the existence, near zero field, of resonant magnetic tunneling between magnetic states of opposite orientation, which are thermally populated.

Ectodysplasin A (EDA)-EDA receptor signalling and its pharmacological modulation

L'ectodysplasine Al (EDA1 ou EDA), un ligand de la famille du TNF, et son récepteur EDAR favorisent le développement des poils, des dents et de plusieurs types de glandes. Chez l'humain, une déficience en EDA cause une dysplasie ectodermique liée à l'X, caractérisée par la genèse défectueuse des phanères. Les souris Tabby, déficientes en Eda, présentent des symptômes similaires. Nous démontrons que les souris Tabby sont en moyenne 7% plus légères que les contrôles au moment du sevrage. Ce phénotype ne dépend pas du génotype des petits, mais exclusivement de celui de la mère, suggérant que l'absence d'EDA perturbe la fonction mammaire. La glande mammaire se développe en plusieurs étapes, principalement à la puberté et pendant la grossesse. Nous avons généré des anticorps pour activer ou inhiber la signalisation d'EDAR. Les anticorps agonistes corrigent le développement de souris ou de chiens déficients en EDA, alors que les antagonistes provoquent une dysplasie ectodermique chez les souris saines. L'exposition répétée de souris Tabby aux anticorps agonistes après le sevrage accroît la taille et la fonction des glandes sébacées, démonstration pharmacologique qu'EDA contrôle l'homéostasie de la glande sébacée adulte. Ces outils seront utiles pour étudier la fonction d'EDA aux diverses étapes du développement de la glande mammaire. Fc-EDAl, un stimulateur d'EDAR, est en phase d'évaluation clinique. Nous avons montré que les structures dépendantes d'EDA qui se forment à différentes étapes du développement répondent à l'action du Fc-EDAl dans des fenêtres temporelles étroites ou larges. De plus, certaines structures peuvent être induites plusieurs jours après le début naturel de leur formation. Alors que la plupart des structures se forment suite à un seul jour d'activation d'EDAR, d'autre demandent un temps de stimulation plus long. La formation des dents est régulée par des signaux activateurs et inhibiteurs. Une forte stimulation d'EDAR spécifiquement appliquée aux deux premières molaires induit des signaux négatifs qui avortent la formation de la troisième molaire, alors qu'une forte stimulation donnée à la troisième molaire la rend hypertrophique tout en induisant parfois une quatrième molaire jamais observée chez les souris de type sauvage ou Tabby. EDA est donc un activateur important de la formation dentaire. Pris dans leur ensemble, ces résultats ont des implications pour la thérapie des dysplasies ectodermiques. - The TNF family ligand Ectodysplasin Al (EDA1 or EDA) and its receptor ED AR regulate embryonic development of hair, teeth and several types of glands. In humans, EDA mutations cause X-linked hypohidrotic ectodermal dysplasia (XLHED), a condition characterized by defective development of skin appendages. £da-deficient (Tabby) mice suffer from similar defects. We observed that Tabby pups at weaning were on average 7% smaller than WT controls, a phenotype that was curiously not linked to the genotype of pups, but to that of mothers, suggesting decreased mammary gland function in the absence of EDA. Mammary glands develop in several steps, most of which are post-natal. We generated monoclonal antibodies to block or activate EDAR signaling. Agonist antibodies rescued developmental defects when administered timely in £cfo-deficient mice and dogs, whereas blocking antibodies induced ectodermal dysplasia in WT mice. Agonist antibodies administered after weaning in £da-deficient mice for several months markedly increased both size and function of sebaceous glands, providing the first demonstration that pharmacological activation of the EDAR pathway in adults can correct important aspects of the dry skin phenotype. This also highlights a role for EDA1 in the homeostasis of adult sebaceous glands. These tools will be useful to study the function of EDA 1 at different stages of mammary gland development. Another EDAR agonist, Fc-EDAl, is currently evaluated in clinical trials. We found that EDA 1-dependent structures forming at different time points during development can respond to Fc-EDAl during time response windows that are narrow or wide. Also, some structures can be triggered up to several days after their normal time of induction. While most structures could be rescued by a single day of EDAR signaling, others required longer exposure times to form. Tooth formation is regulated by activating and inhibitory signals that impact one on the other. When strong EDAR signals were specifically given to the first two molars, overwhelming inhibitory signals completely inhibited formation of the third molar. In contrast, strong signals specifically given to the third molar induced hypertrophy of the later with occasional appearance of a fourth molar never observed in WT or £da-deficient mice. This clearly positions EDA as an important activating signal in tooth formation. Taken together, these results have implications for the therapy of ectodermal dysplasias.

Role of biological agents in auto-inflammatory disease in children

BACKGROUND: Biological agents (BA) have recently completed the treatment options in auto-inflammatory diseases (AID) in children with the aim to improve the outcome. TNF-α blocking agents have been the first BA successfully used in children. However, other biological agents targeting cytokines including IL-1 and IL-6 have been shown to be effective (anti-IL-1/6), especially in AID like systemiconset juvenile arthritis (SoJIA) or cryopyrine-associated periodic syndrome (CAPS). In Switzerland, Etanercept has been approved for the treatment of JIA since 2000 and Canakinumab for the treatment of paediatric CAPS since 2009.OBJECTIVES: Evaluation of the use of biological agents in AID in Western Switzerland.METHODS: We selected all patients with AID seen in the Réseau Romand de Rhumatologie Pédiatrique (Lausanne, Geneva, Aigle, Sion, and Neuchâtel) who were treated with the following BA: anti-TNF-α (Etanercept, Infliximab, Adalimumab) and Abatacept, and anti-IL-1/6 (Anakinra, Canakinumab, Tocilizumab). We looked at minor and major adverse events and the activity of the disease before and after treatment with BA and with special regards on anti-IL-1/6.RESULTS: Among 921 children and adolescents followed between 2004 and 2010, we selected 85 patients with AID (PFAPA: 40, FMF: 6, HyperIgD: 1, CAPS: 3, SoJIA: 34). Only patients with CAPS and SoJIA were treated with BA. They had a mean age of 9 years (3-22) and F: M ratio of 1.6:1. 7 patients were treated with one BA, 6 patients with 2 different BAs and 3 with 3 BAs. 3 patients with CAPS were treated with anti-IL-1 and responded very well. 13 SoJIA patients were treated with BA (anti-TNF-α: 8, Abatacept: 1, anti-IL-1/6: 8). 4 patients treated by anti-TNF-α were switched to anti-IL-1/6 because of lack of response to treatment (cf Table 1). We did not have any serious adverse events and no serious infections.CONCLUSIONS: Patients with SoJIA and CAPS clearly benefit from treatment with BA. General tolerance was good. In the CAPS group the response to IL-1 was excellent. In SoJIA, 3/4 patients, switched from anti-TNF-α to anti-IL-1/6 for lack of therapeutic response, did not respond well to the second medication. These patientsseem to represent a population relatively resistant to treatment with BA. Due to the low number of patients in our cohort, the response to BA in SoJIA patients non-responder to anti- TNF-α agents should be further studied.

Interferon-γ Induces Expression of MHC Class II on Intestinal Epithelial Cells and Protects Mice from Colitis

Immune responses against intestinal microbiota contribute to the pathogenesis of inflammatory bowel diseases (IBD) and involve CD4(+) T cells, which are activated by major histocompatibility complex class II (MHCII) molecules on antigen-presenting cells (APCs). However, it is largely unexplored how inflammation-induced MHCII expression by intestinal epithelial cells (IEC) affects CD4(+) T cell-mediated immunity or tolerance induction in vivo. Here, we investigated how epithelial MHCII expression is induced and how a deficiency in inducible epithelial MHCII expression alters susceptibility to colitis and the outcome of colon-specific immune responses. Colitis was induced in mice that lacked inducible expression of MHCII molecules on all nonhematopoietic cells, or specifically on IECs, by continuous infection with Helicobacter hepaticus and administration of interleukin (IL)-10 receptor-blocking antibodies (anti-IL10R mAb). To assess the role of interferon (IFN)-γ in inducing epithelial MHCII expression, the T cell adoptive transfer model of colitis was used. Abrogation of MHCII expression by nonhematopoietic cells or IECs induces colitis associated with increased colonic frequencies of innate immune cells and expression of proinflammatory cytokines. CD4(+) T-helper type (Th)1 cells - but not group 3 innate lymphoid cells (ILCs) or Th17 cells - are elevated, resulting in an unfavourably altered ratio between CD4(+) T cells and forkhead box P3 (FoxP3)(+) regulatory T (Treg) cells. IFN-γ produced mainly by CD4(+) T cells is required to upregulate MHCII expression by IECs. These results suggest that, in addition to its proinflammatory roles, IFN-γ exerts a critical anti-inflammatory function in the intestine which protects against colitis by inducing MHCII expression on IECs. This may explain the failure of anti-IFN-γ treatment to induce remission in IBD patients, despite the association of elevated IFN-γ and IBD.

Comparative effects of oleoyl-estrone and a specific b3-adrenergic agonist (CL316, 243) on the expression of genes involved in energy metabolism of rat white adipose tissue

Background: The combination of oleoyl-estrone (OE) and a selective b3-adrenergic agonist (B3A; CL316,243) treatment in rats results in a profound and rapid wasting of body reserves (lipid). Methods: In the present study we investigated the effect of OE (oral gavage) and/or B3A (subcutaneous constant infusion) administration for 10 days to overweight male rats, compared with controls, on three distinct white adipose tissue (WAT) sites: subcutaneous inguinal, retroperitoneal and epididymal. Tissue weight, DNA (and, from these values cellularity), cAMP content and the expression of several key energy handling metabolism and control genes were analyzed and computed in relation to the whole site mass. Results: Both OE and B3A significantly decreased WAT mass, with no loss of DNA (cell numbers). OE decreased and B3A increased cAMP. Gene expression patterns were markedly different for OE and B3A. OE tended to decrease expression of most genes studied, with no changes (versus controls) of lipolytic but decrease of lipogenic enzyme genes. The effects of B3A were widely different, with a generalized increase in the expression of most genes, including the adrenergic receptors, and, especially the uncoupling protein UCP1. Discussion: OE and B3A, elicit widely different responses in WAT gene expression, end producing similar effects, such as shrinking of WAT, loss of fat, maintenance of cell numbers. OE acted essentially on the balance of lipolysislipogenesis and the blocking of the uptake of substrates; its decrease of synthesis favouring lipolysis. B3A induced a shotgun increase in the expression of most regulatory systems in the adipocyte, an effect that in the end favoured again the loss of lipid; this barely selective increase probably produces inefficiency, which coupled with the increase in UCP1 expression may help WAT to waste energy through thermogenesis. Conclusions: There were considerable differences in the responses of the three WAT sites. OE in general lowered gene expression and stealthily induced a substrate imbalance. B3A increasing the expression of most genes enhanced energy waste through inefficiency rather than through specific pathway activation. There was not a synergistic effect between OE and B3A in WAT, but their combined action increased WAT energy waste.

mTOR Inhibition and the Tumor Vasculature

Abstract: Blocking tumor growth by targeting the tumor vasculature is a promising approach in cancer therapy. Both, disrupting tumor vessels as well as normalization of tumor vessel abnormalities have shown anti-cancer efficacy. A plethora of agents that act on the tumor vasculature have been developed; however, so far few have shown clinical benefits. Among the successful agents, inhibitors of the mammalian target of rapamycin (mTOR) are able to reduce tumor growth by targeting tumor vessels. mTOR inhibition exerts at least three different effects on the tumor vasculature. First, it reduces tumor angiogenesis. Second it normalizes the tumor vasculature and third, it promotes the formation of thrombosis in tumor vessels. The characterization of the molecular functions regulated by mTOR and of relevance to the tumor vasculature is therefore important in order to further identify biological mechanisms involved in the tumor vascular network as well as to improve the efficacy of these inhibitors. Here, we will first enumerate the evidences for the anti-angiogenic activities of mTOR inhibitors and describe the molecular mechanisms involved. We will further analyze the effects of mTOR inhibition on vascular normalization and also describe how mTOR inhibition promotes thrombosis formation specifically in tumor vessels. Finally, we will describe a new generation of mTOR inhibitors and examine their effects on the tumor vasculature

Podocalyxin is a novel polysialylated neural adhesion protein with multiple roles in neural development and synapse formation

Neural development and plasticity are regulated by neural adhesion proteins, including the polysialylated form of NCAM (PSA-NCAM). Podocalyxin (PC) is a renal PSA-containing protein that has been reported to function as an anti-adhesin in kidney podocytes. Here we show that PC is widely expressed in neurons during neural development. Neural PC interacts with the ERM protein family, and with NHERF1/2 and RhoA/G. Experiments in vitro and phenotypic analyses of podxl-deficient mice indicate that PC is involved in neurite growth, branching and axonal fasciculation, and that PC loss-of-function reduces the number of synapses in the CNS and in the neuromuscular system. We also show that whereas some of the brain PC functions require PSA, others depend on PC per se. Our results show that PC, the second highly sialylated neural adhesion protein, plays multiple roles in neural development.

MHC class I-related chain A conjugated to antitumor antibodies can sensitize tumor cells to specific lysis by natural killer cells.

PURPOSE: As a first step for the development of a new cancer immunotherapy strategy, we evaluated whether antibody-mediated coating by MHC class I-related chain A (MICA) could sensitize tumor cells to lysis by natural killer (NK) cells. EXPERIMENTAL DESIGN: Recombinant MICA (rMICA) was chemically conjugated to Fab' fragments from monoclonal antibodies specific for tumor-associated antigens, such as carcinoembryonic antigen, HER2, or CD20. RESULTS: Flow cytometry analysis showed an efficient coating of MICA-negative human cancer cell lines with the Fab-rMICA conjugates. This was strictly dependent on the expression of the appropriate tumor-associated antigens in the target cells. Importantly, preincubation of the tumor cells with the appropriate Fab-rMICA conjugate resulted in NK cell-mediated tumor cell lysis. Antibody blocking of the NKG2D receptor in NK cells prevented conjugate-mediated tumor cell lysis. CONCLUSIONS: These results open the way to the development of immunotherapy strategies based on antibody-mediated targeting of MICA.

Involvement of the RasGAP derived fragment N in the resistance of pancreatic beta cells towards apoptosis

RESUME DESTINE AUX NON SCIENTIFIQUESLe diabète est une maladie associée à un excès de glucose (sucre) dans le sang. Le taux de glucose sanguin augmente lorsque l'action d'une hormone, l'insuline, responsable du transport du glucose du sang vers les tissus de l'organisme diminue, ou lorsque les quantités d'insuline à disposition sont inadéquates.L'une des causes communes entre les deux grands types de diabète connus, le type 1 et le type 2, est la disparition des cellules beta du pancréas, spécialisées dans la sécrétion d'insuline, par mort cellulaire programmée aussi appelée apoptose. Alors que dans le diabète de type 1, la destruction des cellules beta est causée par notre propre système immunitaire, dans le diabète de type 2, la mort de ces cellules, est principalement causée par des concentrations élevées de graisses saturés ou de molécules impliquées dans l'inflammation que l'on rencontre en quantités augmentées chez les personnes obèses. Etant donné l'augmentation épidémique du nombre de personnes obèses de par le monde, on estime que le nombre de personnes diabétiques (dont une majorité sont des diabétiques de type 2), va passer de 171 million en l'an 2000, à 366 million en l'an 2030, expliquant la nécessité absolue de mettre au point de nouvelles stratégies thérapeutique pour combattre cette maladie.L'apoptose est un processus complexe dont la dérégulation induit de nombreuses affections allant du cancer jusqu'au diabète. L'activation de caspase 3, une protéine clé contrôlant la mort cellulaire, était connue pour systématiquement mener à la mort cellulaire programmée. Ces dernières années, notre laboratoire a décrit des mécanismes de survie qui sont activés par caspase 3 et qui expliquent sans doute pourquoi son activation ne mène pas systématiquement à la mort cellulaire. Lorsqu'elle est faiblement activée, caspase 3 clive une autre protéine appelée RasGAP en deux protéines plus courtes dont l'une, appelée le fragment Ν a la particularité de protéger les cellules contre l'apoptose.Durant ma thèse, j'ai été impliqué dans divers projets destinés à mieux comprendre comment le fragment Ν protégeait les cellules contre l'apoptose et à savoir s'il pouvait être utilisé comme outil thérapeutique dans les conditions de survenue d'un diabète expérimental. C'est dans ce but que nous avons créé une souris transgénique, appelée RIP-N, exprimant le fragment Ν spécifiquement dans les cellules beta. Comme attendu, les cellules beta de ces souris étaient plus résistantes à la mort induite par des composés connus pour induire le diabète, comme certaines molécules induisant l'inflammation ou les graisses saturées. Nous avons ensuite pu montrer que les souris RIP-N étaient plus résistantes à la survenue d'un diabète expérimental que ce soit par l'injection d'une drogue induisant l'apoptose des cellules beta, que ce soit dans un fond génétique caractérisé par une attaque spontanée des cellules beta par le système immunitaire ou dans le contexte d'un diabète de type 2 induit par l'obésité. Dans plusieurs des modèles animaux étudiés, nous avons pu montrer que le fragment Ν protégeait les cellules en activant une voie protectrice bien connue impliquant successivement les protéines Ras, PI3K et Akt ainsi qu'en bloquant la capacité d'Akt d'activer le facteur NFKB, connu pour être délétère pour la survie de la cellule beta. La capacité qu'a le fragment Ν d'activer Akt tout en prévenant l'activation de NFKB par Akt est par conséquent particulièrement intéressante dans l'intégration des signaux régulant la mort cellulaire dans le contexte de la survenue d'un diabète.La perspective d'utiliser le fragment Ν comme outil thérapeutique dépendra de notre capacité à activer les signaux protecteurs induits par le fragment Ν depuis l'extérieur de la cellule ou de dériver des peptides perméables aux cellules possédant les propriétés du fragment N.2 SUMMARYDiabetes mellitus is an illness associated with excess blood glucose. Blood glucose levels raise when the action of insulin decreases or when insulin is provided in inappropriate amounts. In type 1 diabetes (T1D) as well as in type 2 diabetes (T2D), the insulin secreting beta cells in the pancreas undergo controlled cell death also called apoptosis. Whereas in T1D, beta cells are killed by the immune system, in T2D, they are killed by several factors, among which are increased blood glucose levels, increased levels of harmful lipids or pro-inflammatory cytokines that are released by the dysfunctional fat tissue of obese people. Given the epidemic increase in the number of obese people throughout the world, the number of diabetic people (a majority of which are type 2 diabetes) is estimated to rise from 171 million affected people in the year 2000 to 366 million in 2030 explaining the absolute requirement for new therapies to fight the disease.Apoptosis is a very complex process whose deregulation leads to a wide range of diseases going from cancer to diabetes. Caspase 3 although known as a key molecule controlling apoptosis, has been shown to have various other functions. In the past few years, our laboratory has described a survival mechanism, that takes place at low caspase activity and that might explain how cells that activate their caspases for reasons other than apoptosis survive. In such conditions, caspase 3 cleaves another protein called RasGAP into two shorter proteins, one of which, called fragment N, protects cells from apoptosis.We decided to check whether fragment Ν could be used as a therapeutical tool in the context of diabetes inducing conditions. We thus derived a transgenic mouse line, called RIP-N, in which the expression of fragment Ν is restricted to beta cells. As expected, the beta cells of these mice were more resistant ex-vivo to cell death induced by diabetes inducing factors. We then showed that the RIP-N transgenic mice were resistant to streptozotocin induced diabetes, a mouse model mimicking type 1 diabetes, which correlated to fewer number of apoptotic beta cells in the pancreas of the transgenic mice compared to their controls. The RIP-N transgene also delayed overt diabetes development in the NOD background, a mouse model of autoimmune type 1 diabetes, and delayed the occurrence of obesity induced hyperglycemia in a mouse model of type 2-like diabetes. Interestingly, fragment Ν was mediating its protection by activating the protective Akt kinase, and by blocking the detrimental NFKB factor. Our future ability to activate the protective signals elicited by fragment Ν from the outside of cells or to derive cell permeable peptides bearing the protective properties of fragment Ν might condition our ability to use this protein as a therapeutic tool.3 RESUMELe diabète est une maladie associée à un excès de glucose plasmatique. La glycémie augmente lorsque l'action de l'insuline diminue ou lorsque les quantités d'insuline à disposition sont inadéquates. Dans le diabète de type 1 (D1) comme dans le diabète de type 2 (D2), les cellules beta du pancréas subissent la mort cellulaire programmée aussi appelée apoptose. Alors que dans le D1 les cellules beta sont tuées par le système immunitaire, dans le D2 elles sont tuées par divers facteurs parmi lesquels on trouve des concentrations élevées de glucose, d'acides gras saturés ou de cytokines pro-inflammatoires qui sont sécrétées en concentrations augmentées par le tissu adipeux dysfonctionnel des personnes obèses. Etant donné l'augmentation épidémique du nombre de personnes obèses de par le monde, on estime que le nombre de personnes diabétiques (dont une majorité sont des diabétiques de type 2), va passer de 171 million en l'an 2000, à 366 million en l'an 2030, justifiant la nécessité absolue de mettre au point de nouvelles stratégies thérapeutique pour combattre cette maladie.L'apoptose est un processus complexe dont la dérégulation induit de nombreuses affections allant du cancer jusqu'au diabète. Caspase 3, bien que connue comme étant une protéine clé contrôlant l'apoptose a bien d'autres fonctions démontrées. Ces dernières années, notre laboratoire a décrit un mécanisme de survie qui est activé lorsque caspase 3 est faiblement activée et qui explique probablement comment des cellules qui ont activé leurs caspases pour une autre raison que l'apoptose peuvent survivre. Dans ces conditions, caspase 3 clive une autre protéine appelée RasGAP en deux protéines plus courtes dont l'une, appelée le fragment Ν a la particularité de protéger les cellules contre l'apoptose.Nous avons donc décidé de vérifier si le fragment Ν pouvait être utilisé comme outil thérapeutique dans les conditions de survenue d'un diabète expérimental. Pour se faire, nous avons créé une souris transgénique, appelée RIP-N, exprimant le fragment Ν spécifiquement dans les cellules beta. Comme attendu, les cellules beta de ces souris étaient plus résistantes ex-vivo à la mort induite par des facteurs pro-diabétogènes. Nous avons ensuite pu montrer que les souris RIP-N étaient plus résistantes à la survenue d'un diabète induit par la streptozotocine, un drogue mimant la survenue d'un D1 et que ceci était corrélée à une diminution du nombre de cellules en apoptose dans le pancréas des souris transgéniques comparé à leurs contrôles. L'expression du transgène a aussi eu pour effet de retarder la survenue d'un diabète franc dans le fond génétique NOD, un modèle génétique de diabète de type 1 auto-immun, ainsi que de retarder la survenue d'une hyperglycémie dans un modèle murin de diabète de type 2 induit par l'obésité. Dans plusieurs des modèles animaux étudiés, nous avons pu montrer que le fragment Ν protégeait les cellules en activant la kinase protectrice Akt ainsi qu'en bloquant le facteur délétère NFKB. La perspective d'utiliser le fragment Ν comme outil thérapeutique dépendra de notre capacité à activer les signaux protecteurs induits par le fragment Ν depuis l'extérieur de la cellule ou de dériver des peptides perméables aux cellules possédant les propriétés du fragment

Excitotoxicity-induced endocytosis mediates neuroprotection by TAT-peptide-linked JNK inhibitor.

ABSTRACT: Excitotoxicity and cerebral ischemia induce strong endocytosis in neurons, and we here investigate its functional role in neuroprotection by a functional transactivator of transcription (TAT)-peptide, the c-Jun N-terminal kinase (JNK) inhibitor D-JNKI1, against NMDA-excitotoxicity in vitro and neonatal ischemic stroke in P12 Sprague-Dawley rats. In both situations, the neuroprotective efficacy of D-JNKI1 was confirmed, but excessively high doses were counterproductive. Importantly, the induced endocytosis was necessary for neuroprotection, which required that the TAT-peptide be administered at a time when induced endocytosis was occurring. Uptake by other routes failed to protect, and even promoted cell death at high doses. Blocking the induced endocytosis of D-JNKI1 with heparin or with an excess of D-TAT-peptide eliminated the neuroprotection. We conclude that excitotoxicity-induced endocytosis is a basic property of stressed neurons that can target neuroprotective TAT-peptides into the neurons that need protection. Furthermore, it is the main mediator of neuroprotection by D-JNKI1. This may explain promising reports of strong neuroprotection by TAT-peptides without apparent side effects, and warns that the timing of peptide administration is crucial.

Expression of calbindin immunoreactivity by subpopulations of primary sensory neurons in chick embryo dorsal root ganglion cells grown in coculture or conditioned medium.

Primary sensory neurons which innervate neuromuscular spindles in the chicken are calbindin-immunoreactive. The influence exerted by developing skeletal muscle on the expression of calbindin immunoreactivity by subpopulations of dorsal root ganglion (DRG) cells in the chick embryo was tested in vitro in coculture with myoblasts, in conditioned medium (CM) prepared from myoblasts and in control cultures of DRG cells alone. Control cultures of DRG cells grown at the 6th embryonic day (E6) did not show any calbindin-immunostained ganglion cell. In coculture of myoblasts previously grown for 14 days, about 3% of calbindin-immunoreactive ganglion cells were detected while about 1% were observed in some cultures grown in CM. Fibroblasts from various sources were devoid of effect. Skin or kidney cells were more active than myoblasts to initiate calbindin expression by subpopulations of DRG cells in coculture or, to a lesser degree, in CM. The results suggest that cellular factors would rather induce calbindin expression in certain sensory neurons than ensure a selective neuronal survival.

Single-fiber electromyography of the laryngeal muscles.

Single-fiber electromyography (SFEMG) is useful in the evaluation of disorders of neuromuscular transmission and the assessment of motor unit morphology. Standard EMG techniques are used routinely in the evaluation of laryngeal dysfunction, but the feasibility of laryngeal SFEMG has not been established. We, therefore, performed laryngeal SFEMG in 10 normal individuals to demonstrate the feasibility of the technique and generate preliminary normative data. We also studied 2 patients with amyotrophic lateral sclerosis and 1 patient previously treated with botulinum toxin for comparative purposes.

Deficiency in monocarboxylate transporter 1 (MCT1) in mice delays regeneration of peripheral nerves following sciatic nerve crush.

Peripheral nerve regeneration following injury occurs spontaneously, but many of the processes require metabolic energy. The mechanism of energy supply to axons has not previously been determined. In the central nervous system, monocarboxylate transporter 1 (MCT1), expressed in oligodendroglia, is critical for supplying lactate or other energy metabolites to axons. In the current study, MCT1 is shown to localize within the peripheral nervous system to perineurial cells, dorsal root ganglion neurons, and Schwann cells by MCT1 immunofluorescence in wild-type mice and tdTomato fluorescence in MCT1 BAC reporter mice. To investigate whether MCT1 is necessary for peripheral nerve regeneration, sciatic nerves of MCT1 heterozygous null mice are crushed and peripheral nerve regeneration was quantified electrophysiologically and anatomically. Compound muscle action potential (CMAP) recovery is delayed from a median of 21days in wild-type mice to greater than 38days in MCT1 heterozygote null mice. In fact, half of the MCT1 heterozygote null mice have no recovery of CMAP at 42days, while all of the wild-type mice recovered. In addition, muscle fibers remain 40% more atrophic and neuromuscular junctions 40% more denervated at 42days post-crush in the MCT1 heterozygote null mice than wild-type mice. The delay in nerve regeneration is not only in motor axons, as the number of regenerated axons in the sural sensory nerve of MCT1 heterozygote null mice at 4weeks and tibial mixed sensory and motor nerve at 3weeks is also significantly reduced compared to wild-type mice. This delay in regeneration may be partly due to failed Schwann cell function, as there is reduced early phagocytosis of myelin debris and remyelination of axon segments. These data for the first time demonstrate that MCT1 is critical for regeneration of both sensory and motor axons in mice following sciatic nerve crush.